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An anti-ErbB2 fully human antibody circumvents trastuzumab resistance.

ABSTRACT: Trastuzumab, an anti-HER2/ErbB2 humanized antibody, has shown great clinical benefits in ErbB2-positive breast cancer treatment. Despite of its effectiveness, response rate to trastuzumab is limited and resistance is common. Here, we developed a new anti-ErbB2 antibody, denoted as H2-18, which was isolated from a phage display human antibody library. Previous studies have demonstrated that trastuzumab recognizes the juxtamembrane region of domain IV, and pertuzumab, another humanized ErbB2-specific antibody, binds to ErbB2 near the center of domain II. Our crystallographic analysis showed that the epitope recognized by H2-18 is within domain I of the ErbB2 molecule. H2-18 potently induced programmed cell death (PCD) in both trastuzumab-sensitive and -resistant breast cancer cell lines, while trastuzumab and pertuzumab, either used alone or in combination, only exhibits very weak PCD-inducing activity. More importantly, H2-18 could inhibit the growth of trastuzumab-resistant breast cancer cells far more effectively than trastuzumab plus pertuzumab, both in vitro and in vivo. In conclusion, H2-18 shows a unique ability to overcome trastuzumab resistance, suggesting that it has the great potential to be translated to the clinic.

SUBMITTER: Lu Q

PROVIDER: S-EPMC5341862 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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An anti-ErbB2 fully human antibody circumvents trastuzumab resistance.

Lu Qiong Q Wang Lingfei L Zhang Yajun Y Yu Xiaojie X Wang Chao C Wang Huajing H Yang Yang Y Chong Xiaodan X Xia Tian T Meng Yanchun Y Wang Yuxiao Y Lu Cuihua C Zhou Lijun L Li Bohua B

Oncotarget 20161001 41

Trastuzumab, an anti-HER2/ErbB2 humanized antibody, has shown great clinical benefits in ErbB2-positive breast cancer treatment. Despite of its effectiveness, response rate to trastuzumab is limited and resistance is common. Here, we developed a new anti-ErbB2 antibody, denoted as H2-18, which was isolated from a phage display human antibody library. Previous studies have demonstrated that trastuzumab recognizes the juxtamembrane region of domain IV, and pertuzumab, another humanized ErbB2-speci ...[more]

PMID: 27564098

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Project description:Trastuzumab resistance is a severe problem in the treatment of ErbB2-amplified cancer. Although trastuzumab plus pertuzumab is able to partly overcome trastuzumab resistance in ErbB2-overexpressing cancer, its antitumor efficacy remains limited. The present study investigated the antitumor activity of the combination of trastuzumab with H2-18, which is an antibody targetinsg ErbB2 domain I. Cell proliferation and inhibition experiments indicated that H2-18 and trastuzumab synergistically inhibited the proliferation of both the trastuzumab-sensitive gastric cancer cell line, NCI-N87 and the trastuzumab-resistant gastric cancer cell line, NCI-N87-TraRT. Furthermore, H2-18 plus trastuzumab inhibited the growth of NCI-N87-TraRT cells more effectively than trastuzumab plus pertuzumab, both in vitro and in vivo. Compared with trastuzumab plus pertuzumab, H2-18 plus trastuzumab had a potent ability to inhibit NCI-N87-TraRT cells to form colonies. Notably, H2-18 plus trastuzumab was more effective in inducing cell death than trastuzumab plus pertuzumab. The in vivo studies demonstrated that H2-18 plus trastuzumab effectively inhibited the growth of both NCI-N87 and NCI-N87-TraRT xenograft tumors. Further experiments revealed that in NCI-N87-TraRT cells, H2-18 plus trastuzumab was comparable to trastuzumab plus pertuzumab in the inhibition of phosphorylated (p-)HER3, p-AKT and p-ERK. However, compared with trastuzumab plus pertuzumab, H2-18 plus trastuzumab effectively activated ROS production and the phosphorylation of JNK and c-jun in NCI-N87-TraRT cells. Therefore, the superior antitumor efficacy of H2-18 plus trastuzumab over trastuzumab plus pertuzumab may be mainly attributable to the potent cell death-inducing activity. In addition, the in vitro and in vivo antitumor effect of the combination of H2-18, trastuzumab and pertuzumab were further investigated. The results revealed that H2-18 plus trastuzumab plus pertuzumab exhibited a maximal antitumor effect among all the anti-ErbB2 monoclonal antibody combinations tested. In summary, H2-18 plus trastuzumab may have potential as an effective strategy to overcome the resistance to trastuzumab in ErbB2-amplified gastric cancer cell lines.

Project description:Targeted therapy using monoclonal antibodies conjugated to toxins is gaining space in the treatment of cancer. Here, we report the anti-tumor effect of a new antibody drug conjugate (ADC) delivering a HDAC inhibitor to ErbB2+ solid tumors. Trastuzumab was partially reduced with tris [2-carboxyethyl] phosphine (TCEP) and conjugated to ST7464AA1, the active form of the prodrug HDAC inhibitor ST7612AA1, through a maleimide-thiol linker to obtain the Antibody Drug Conjugate (ADC) ST8176AA1. The average drug/antibody ratio (DAR) was 4.5 as measured by hydrophobic interaction chromatography (HIC). Binding of ST8176AA1 to ErbB2 receptor and internalization in tumor cells were investigated by enzyme-linked immunosorbent assay (ELISA), surface plasmon resonance (SPR), cytofluorimetry, and High Content Screening (HCS) Imaging. The biological activity of the ADC was evaluated in vitro and in vivo by measuring cell proliferation/cell cycle, apoptosis/DNA damage, tubulin, and histone acetylation and modulation of Epithelial/Mesenchymal Transition (EMT) markers. Receptor binding and internalization of ST8176AA1 were confirmed to be similar to trastuzumab. Higher anti-tumor activity of ST8176AA1 compared to trastuzumab was observed in vitro in tumor cell lines. Such higher activity correlated with increased acetylation of histones and alfa-tubulin as a consequence of HDAC inhibitor-mediated epigenetic modulation that also induced increased expression of ErbB2 and estrogen receptor in triple negative breast cancer cells. Consistently with in vitro data, ST8176AA1 exhibited higher tumor growth inhibition than trastuzumab in xenograft models of ovary and colon carcinoma and in two patient-derived xenograft (PDX) models of pancreatic carcinoma. Immunohistochemistry analysis of tumor masses showed lower expression of the proliferation marker Ki67 and higher expression of cleaved caspase-3 in mice treated with the ADC compared to those treated with trastuzumab and results correlated with increased acetylation of both histones and tubulin. Collectively, present data indicate that ADC ST8176AA1 can target epigenetic modulation to ErbB2+ tumors. Interestingly, the amount of HDACi estimated to be delivered at the ST8176AA1 effective dose would correspond to ~1/1,000 of ST7612AA1 effective dose. Therefore, ST8176AA1 is an attractive new therapeutic candidate because it exhibits increased anti-tumor potency compared to trastuzumab by exerting epigenetic modulation at a much safer dose compared to standard HDACi-based therapeutic protocols.

Project description:Autophagy has been emerging as a novel cytoprotective mechanism to increase tumor cell survival under conditions of metabolic stress and hypoxia as well as to escape chemotherapy-induced cell death. To elucidate whether autophagy might also protect cancer cells from the growth inhibitory effects of targeted therapies, we evaluated the autophagic status of preclinical breast cancer models exhibiting auto-acquired resistance to the anti-HER2 monoclonal antibody trastuzumab (Tzb). We first examined the basal autophagic levels in Tzb-naive SKBR3 cells and in two pools of Tzb-conditioned SKBR3 cells (TzbR), which optimally grow in the presence of Tzb doses as high as 200 microg/ml Tzb. Fluorescence microscopic analyses revealed that the number of punctate LC3 structures -a hallmark of autophagy- was drastically higher in Tzb-refractory cells than in Tzb-sensitive SKBR3 parental cells. Immunoblotting analyses confirmed that the lipidation product of the autophagic conversion of LC3 was accumulated to high levels in TzbR cells. High levels of the LC3 lipidated form in Tzb-refractory cells were accompanied by decreased p62/sequestosome-1 protein expression, a phenomenon characterizing the occurrence of increased autophagic flux. Moreover, increased autophagy was actively used to survive Tzb therapy as TzbR pools were exquisitely sensitive to chemical inhibitors of autophagosomal formation/function. Knockdown of LC3 expression via siRNA similarly resulted in reduced TzbR cell proliferation and supra-additively interacted with Tzb to re-sensitize TzbR cells. Sub-groups of Tzb-naive SKBR3 parental cells accumulated LC3 punctate structures and decreased p62 expression after treatment with high-dose Tzb, likely promoting their own resistance. This is the first report showing that HER2-overexpressing breast cancer cells chronically exposed to Tzb exhibit a bona fide up-regulation of the autophagic activity that efficiently works to protect breast cancer cells from the growth-inhibitory effects of Tzb. Therapeutic targeting autophagosome formation/function might represent a novel molecular avenue to reduce the emergence of Tzb resistance in HER2-dependent breast carcinomas.

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An anti-ErbB2 fully human antibody circumvents trastuzumab resistance.

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An anti-ErbB2 fully human antibody circumvents trastuzumab resistance.

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